/Engine/Source/Editor/UnrealEd/Public/UnrealEdMisc.h
Finds a map using only the map name, no extension, no path, also caches it for faster lookup next time.
[FString](API\Runtime\Core\Containers\FString) FindMapFileFromPartialName ( const [FString](API\Runtime\Core\Containers\FString) & PartialMapName )